What kind of gap ? If quite a small gap it is usually fine to go straight through plasterboard and install anchors in concrete behind.
There are many options, which would vary depending on size and weight of TV.
Nylon wall/fischer plugs for light/small TVs. May have issues with depth in this case.
These then come in larger versions with coach bolts.
As you get bigger you can use expanding anchors, some are stud type, some are threaded sleaves.
I personally like screw in anchors which is another option.
Lastly chemical set anchors.
If masonry you will likely need an SDS masonry bit and a rotary hammer drill. Then depending on anchor type, may need a hammer and screwdriver or spanner/ratchet.
If there is a large gap with a stud ideally just try and pick up the stud and screw to that, if your TV is small enough that it's between studs it may be small and light enough to only pickup one stud or use expanding anchors/toggles.
If a large TV try and straddle 2 or more studs, if need be you can install say for example a small wood or MDF panel painted or with coating/laminate to suit your wall that goes across the studs and spreads the load, this then allows the mount to be installed anywhere on the panel and with large TVs this panel is covered/not really noticeable.
These options generally require a drill and screwdriver.